We propose to recover cells from NP swab samples and sort individual cells of different subsets based on specific surface phenotypic markers. We will then utilize microfluidics-based real-time reverse transcriptase polymerase chain reaction (rRT-PCR) to quantify transcripts from bulk and single cells. These transcripts will include strand-specific influenza RNA for determining virus replication, genes for assigning cells to specific epithelial or lymphocyte subpopulations, selected genes in the IFN signaling pathways to determine innate immune responses, and genes involved in activation and effector functions of different immune cell subsets. Results will be analyzed with several bioinformatics tools, with an emphasis on the differential signaling responses between various cells types. The mucosal transcriptional data will be correlated with B and T cell immunity markers and traditional serology (HAI and neutralization assays) before and after vaccination to identify key factors affecting the immune response to LAIV.